1. Field of the Invention
The present invention relates to a liquid crystal display module in which a backlight is mounted, and particularly to a technique suitable for use in a small liquid crystal display module used for a mobile phone and the like.
2. Description of the Related Art
FIG. 9 is a diagram showing a cross sectional configuration of main components of a conventional liquid crystal display module.
A liquid crystal display panel is configured in such a manner that a liquid crystal layer (not shown) is sandwiched between a TFT substrate 11 and a color filter substrate 12 (hereinafter, referred to as CF substrate 12). The TFT substrate 11 is larger than the CF substrate 12 in size, and a driver chip 13 for controlling the driving of the liquid crystal display panel is arranged at a region, on the TFT substrate 11, that is not overlapped with the CF substrate 12. Further, an upper polarization plate 14 is arranged on the CF substrate 12, and a lower polarization plate 20 is arranged under the TFT substrate 11. Furthermore, a backlight is arranged under the liquid crystal display panel so as to configure a liquid crystal display module.
The backlight is configured by a light source 18 such as an LED arranged on a flexible print substrate 15 (hereinafter, referred to as FPC 15), and a light guide plate 17 through which light emitted from the light source 18 is guided to the entire liquid crystal display panel. Optical sheets 22 are arranged between the light guide plate 17 and the liquid crystal display panel. The optical sheets include, for example, an upper diffusion sheet, an upper prism sheet, a lower prism sheet, a lower diffusion sheet, and the like. A reflection sheet 23 is arranged under the light guide plate 17 so as to function to direct light guided under the light guide plate 17 toward the liquid crystal display panel. In order to satisfy the requirements of a thinner liquid crystal display apparatus, the light guide plate 17 is configured to be thinner except for an incident face opposed to the light source 18. Because the size of an LED that is suitable at present as the light source 18 is large, the thickness of the incident face is configured to be large. The incident face of the light guide plate 17 is configured to be large in size in accordance with the size of the LED. In FIG. 9, the reference numeral 16 denotes a mold frame, and the liquid crystal display module is configured in such a manner that the liquid crystal display panel is arranged above the frame-like mold frame and the backlight is arranged thereunder.
As shown in FIG. 9, a light shielding tape 31 is arranged on the TFT substrate 11 on the side where the lower polarization plate 20 is arranged and at a position above the light source 18. Further, a spacer tape 91 which has an L-shaped cross section as shown in FIG. 10 and which is configured by, for example, a white PET is arranged on the light shielding tape 31 so that unnecessary light is prevented from entering the liquid crystal display panel.
JP-A No. 1995-294921 is one of well-known techniques which describes a liquid crystal display module in which an incident face of the light guide plate is thus configured to be large.
In the case of the configuration shown in FIG. 9, a space 90 is formed between the light guide plate 17 and the spacer tape 91, and thus it has been found that a problem arises in that the space 90 causes the loss of light.
In view of the above-described problem, an object of the present invention is to provide a liquid crystal display module that eliminates the loss of light emitted from a light source.